Preliminary measurements have been made of oxygen equilibrium in dilute and concentrated solutions of normal and sickle hemoglobin. A mechanism for the desolubilization of sickle hemoglobin by nonaggregating proteins has been formulated. The binding of peanut agglutinin to synthetic carbohydrate-containing model systems is being experimentally studied. The self-association of myoglobin in concentrated solution is being experimentally studied. The effect of binding site heterogeneity upon the ligand binding equilibria and kinetics of cells and cell membranes has been theoretically studied. The exclusion of proteins from solutions containing polyethylene glycol is being theoretically studied. The effect of particle shape and size upon thermodynamic activity in heterogeneous systems is being theoretically studied.